[SiriusHardware]

It sounds as though the system is kind of working when you say holding down a key makes the system make a noise.

What if you just hold down and then release CTRL and G together, does that make a noise? (you may need to press/release CAPS LOCK once first, if the machine has a CAPS LOCK key). Not knowing the machine well I can't guarantee that will work on a PET, but if it does work that will be useful to know.

Making a test EPROM, yes, good idea but no matter which one you make (I would suggest Daver2's test code as that can be programmed into a 2716 which will drop straight in) you will need a working display in order to see the output it generates, so, while a useful tool to have, you will not be able to use it until you have a working monitor.

Even if the PET has been switched off for days the tube will still be holding a full charge, in fact it will hold the charge indefinitely until it is intentionally discharged. After looking at various videos etc we think your best way to get at the measurement points on the monitor would be to unmount the whole monitor housing from the main plinth and lie it on its side so you can get to most of the underside of the monitor PCB through the 'Hatch' underneath. If you can take the monitor housing and its works off the plinth in one piece then you should not need to dismount the monitor PCB from inside the monitor housing at this stage.

Alternatively turn the whole machine onto one side and open the two halves of the case (upper and lower) up to 90 degrees apart, if that allows you access to the monitor PCB test points AJ and I indicated in earlier posts.

Have you given any consideration to Courtney's offer to look at it? We will assist you as much as we can for however long it takes but there is no substitute for having someone who knows their way around the machine sitting in front of it, and Courtney could easily try plugging the monitor of one of her working machines into your mainboard to see if your mainboard is producing video output, which we suspect it is. I don't know Courtney personally but I have the impression from reading her past posts that she has a lot of experience with all sorts of retro tech including CRT displays.